Changeset 14805

Timestamp:

May 20, 2011, 2:59:00 AM (14 years ago)

Author:

Gary Byers

Message:

In _SPcallback, save the caller's mxcsr on and restore it from the
stack, not in tcr.foreign_mxcsr. Different callers can legitimately
have different mxcsr values (as long as they save/restore the mxcsr
before changing its value), and we want callbacks to restore the caller's
value (not that of the most recent callback on the thread.)

callback_to_lisp() in the CCL kernel is an example of a C function that
calls into lisp with an atypical value in the mxcsr. It's not clear
that that's a useful value, but callback_to_lisp() saves/restores the
mxcsr before setting it to that value.

Reported problems which are symptoms of the mxcsr getting trashed in
the IDE seem to stem from the fact that callback_to_lisp() invokes a
callback with this atypical mxcsr value when unresolved EEPs are used
from callbacks. We might want to change callback_to_lisp() to not do
that, but the problem is and always has been that callbacks don't
restore the mxcsr that they were called with. The treatment of
the mxcsr by _SPffcall (and the behavior of callback_to_lisp()) just
exposed that problem.

File:

• trunk/source/lisp-kernel/x86-spentry64.s (modified) (3 diffs)

trunk/source/lisp-kernel/x86-spentry64.s

@@ -4617 +4617 @@
         __ifndef(`WINDOWS')
         __endif
+        /* Save caller's mxcsr */
+        __(subq $16,%rsp)
+        __(stmxcsr (%rsp))
+        __(andb $~mxcsr_all_exceptions,(%rsp))
         /* C NVRs   */
         __(push %csave0)
@@ -4685 +4689 @@
          __(movq 24(%rsp),%save3)
         __endif
-        __(stmxcsr rcontext(tcr.foreign_mxcsr))
-        __(andb $~mxcsr_all_exceptions,rcontext(tcr.foreign_mxcsr))
         __(ldmxcsr rcontext(tcr.lisp_mxcsr))
         __(movq $nrs.callbacks,%fname)
@@ -4717 +4719 @@
         __(pop %csave1)
         __(pop %csave0)
+        __(ldmxcsr (%rsp))
+        __(addq $16,%rsp)
         __(movq -8(%rbp),%rax)
         __(movq -16(%rbp),%rdx)